Here's why:
* The Missouri River originates in the Rocky Mountains, specifically in the state of Montana.
* It then flows eastward, passing through states like North Dakota, South Dakota, Nebraska, Kansas, Iowa, and Missouri.
* The Rocky Mountain region encompasses states like Montana, Idaho, Wyoming, Colorado, Utah, and New Mexico. While the Missouri River originates in the Rocky Mountains, it doesn't flow through any other states in the region after that.
